Pneumatic motor

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Victor Tatin's 1879 Aeroplane used a compressed-air engine for propulsion. Original craft, at Musee de l'Air et de l'Espace. Victor Tatin aeroplane 1879.jpg
Victor Tatin's 1879 Aéroplane used a compressed-air engine for propulsion. Original craft, at Musée de l'Air et de l'Espace.
The first mechanically powered submarine, the 1863 French submarine Plongeur, used a compressed-air engine. Musee de la Marine (Rochefort). Plongeur Rochefort top and side views.jpg
The first mechanically powered submarine, the 1863 French submarine Plongeur , used a compressed-air engine. Musée de la Marine (Rochefort).

A pneumatic motor (air motor), or compressed-air engine, is a type of motor which does mechanical work by expanding compressed air. Pneumatic motors generally convert the compressed-air energy to mechanical work through either linear or rotary motion. Linear motion can come from either a diaphragm or piston actuator, while rotary motion is supplied by either a vane type air motor, piston air motor, air turbine or gear type motor.

Contents

Pneumatic motors have existed in many forms over the past two centuries, ranging in size from hand-held motors to engines of up to several hundred horsepower. Some types rely on pistons and cylinders; others on slotted rotors with vanes (vane motors) and others use turbines. Many compressed-air engines improve their performance by heating the incoming air or the engine itself. Pneumatic motors have found widespread success in the hand-held tool industry, [1] but are also used stationary in a wide range of industrial applications. Continual attempts are being made to expand their use to the transportation industry. However, pneumatic motors must overcome inefficiencies before being seen as a viable option in the transportation industry.

Classification

Linear

In order to achieve linear motion from compressed air, a system of pistons is most commonly used. The compressed air is fed into an air-tight chamber that houses the shaft of the piston. Also inside this chamber a spring is coiled around the shaft of the piston in order to hold the chamber completely open when air is not being pumped into the chamber. As air is fed into the chamber the force on the piston shaft begins to overcome the force being exerted on the spring. [2] As more air is fed into the chamber, the pressure increases and the piston begins to move down the chamber. When it reaches its maximum length the air pressure is released from the chamber and the spring completes the cycle by closing off the chamber to return to its original position.

Piston motors are the most commonly used in hydraulic systems. Essentially, piston motors are the same as hydraulic motors except they are used to convert hydraulic energy into mechanical [3] energy. [4]

Piston motors are often used in series of two, three, four, five, or six cylinders that are enclosed in a housing. This allows for more power to be delivered by the pistons because several motors are in sync with each other at certain times of their cycle.

The practical mechanical efficiencies attained by a piston air motor are between 40–50%. [5]

The Robot Robothespian with linear motors in its biceps Campus Party Europa Dia 2 (4523750986).jpg
The Robot Robothespian with linear motors in its biceps

Rotary vane motors

Vane-type-motor Vane-type-motor.svg
Vane-type-motor

A type of pneumatic motor, known as a rotary vane motor, uses air to produce rotational motion to a shaft. The rotating element is a slotted rotor which is mounted on a drive shaft. Each slot of the rotor is fitted with a freely sliding rectangular vane. [4] The vanes are extended to the housing walls using springs, cam action, or air pressure, depending on the motor design. Air is pumped through the motor input which pushes on the vanes creating the rotational motion of the central shaft. Rotation speeds can vary between 100 and 25,000 rpm depending on several factors which include the amount of air pressure at the motor inlet and the diameter of the housing. [2]

One application for vane-type air motors is to start large industrial diesel or natural gas engines. Stored energy in the form of compressed air, nitrogen or natural gas enters the sealed motor chamber and exerts pressure against the vanes of a rotor. This causes the rotor to turn at high speed. Because the engine flywheel requires a great deal of torque to start the engine, reduction gears are used. Reduction gears create high torque levels with the lower amounts of energy input. These reduction gears allow for sufficient torque to be generated by the engine flywheel while it is engaged by the pinion gear of the air motor or air starter.

Turbine motors

Air turbines spin the burr in high-speed dental handpieces, at speeds over 180,000 rpm, but with limited torque. A turbine is small enough to fit in the tip of a handpiece without adding to the weight.

Application

A widespread application of pneumatic motors is in hand-held tools, impact wrenches, pulse tools, screwdrivers, nut runners, drills, grinders, sanders and so on. Pneumatic motors are also used stationary in a wide range of industrial applications. Though overall energy efficiency of pneumatics tools is low and they require access to a compressed-air source, there are several advantages over electric tools. They offer greater power density (a smaller pneumatic motor can provide the same amount of power as a larger electric motor), do not require an auxiliary speed controller (adding to its compactness), generate less heat, and can be used in more volatile atmospheres as they do not require electric power [6] and do not create sparks. They can be loaded to stop with full torque without damages. [7] The efficiency of a rotary piston engine is highly dependent on mechanical energy losses. The value of mechanical losses, according to various estimates, can be 20% of the energy supplied to the engine. [8] At the same time it was experimentally shown that efficiency of a motor can be increased by the usage of anti-friction additives to the lubricating oil. [9]

Historically, many individuals have tried to apply pneumatic motors to the transportation industry. Guy Negre, CEO and founder of Zero Pollution Motors, has pioneered this field since the late 1980s. [10] Recently Engineair has also developed a rotary motor for use in automobiles. Engineair places the motor immediately beside the wheel of the vehicle and uses no intermediate parts to transmit motion which means almost all of the motor's energy is used to rotate the wheel. [11]

History in transportation

The pneumatic motor was first applied to the field of transportation in the mid-19th century. Though little is known about the first recorded compressed-air vehicle, it is said that the Frenchmen Andraud and Tessie of Motay ran a car powered by a pneumatic motor on a test track in Chaillot, France, on 9 July 1840. Although the car test was reported to have been successful, the pair didn't explore further expansion of the design. [12]

The first successful application of the pneumatic motor in transportation was the Mekarski system air engine used in locomotives. Mekarski's innovative engine overcame cooling that accompanies air expansion by heating air in a small boiler prior to use. The Tramway de Nantes, located in Nantes, France, was noted for being the first to use Mekarski engines to power their fleet of locomotives. The tramway began operation on December 13, 1879, and continues to operate today, although the pneumatic trams were replaced in 1917 by more efficient and modern electrical trams.

American Charles Hodges also found success with pneumatic motors in the locomotive industry. In 1911 he designed a pneumatic locomotive and sold the patent to the H.K. Porter Company in Pittsburgh for use in coal mines. [13] Because pneumatic motors do not use combustion they were a much safer option in the coal industry. [12]

Many companies[ who? ] claim to be developing compressed-air cars, but none are actually available for purchase or even independent testing.

Tools

Impact wrenches, pulse tools, torque wrenches, screwdrivers, drills, grinders, die grinders, sanders, dental drills, tire changers and other pneumatic tools use a variety of air motors. These include vane type motors, turbines and piston motors.

Torpedoes

Most successful early forms of self-propelled torpedoes used high-pressure compressed air, although this was superseded by internal or external combustion engines, steam engines (driven by the catalytic decomposition of hydrogen peroxide), or electric motors.

Railways

Compressed-air engines were used in trams and shunters, and eventually found a successful niche in mining locomotives, although in the end they were replaced by electric trains, underground. [14] Over the years designs increased in complexity, resulting in a triple expansion engine with air-to-air reheaters between each stage. [15] For more information see Fireless locomotive and Mekarski system.

Flight

Water rockets use compressed air to power their water jet and generate thrust, they are used as toys.

Air Hogs, a toy brand, also uses compressed air to power piston engines in toy airplanes (and some other toy vehicles).

Automotive

There is currently some interest in developing air cars. Several engines have been proposed for these, although none have demonstrated the performance and long life needed for personal transport.

Energine

The Energine Corporation was a South Korean company that claimed to deliver fully assembled cars running on a hybrid compressed air and electric engine. The compressed-air engine is used to activate an alternator, which extends the autonomous operating capacity of the car. The CEO was arrested for fraudulently promoting air motors with false claims. [17]

EngineAir

EngineAir, an Australian company, is making a rotary engine powered by compressed air, called The Di Pietro motor. The Di Pietro motor concept is based on a rotary piston. Different from existing rotary engines, the Di Pietro motor uses a simple cylindrical rotary piston (shaft driver) which rolls, with little friction, inside the cylindrical stator. [18]

It can be used in boats, cars, burden carriers and other vehicles. Only 1 psi (≈ 6,8 kPa) of pressure is needed to overcome the friction. [19] [20] The engine was also featured on the ABC's New Inventors programme in Australia on 24 March 2004. [21]

K'Airmobiles

K'Airmobiles vehicles were intended to be commercialized from a project developed in France in 2006–2007 by a small group of researchers. However, the project has not been able to gather the necessary funds.

People should note that, meantime, the team has recognized the physical impossibility to use on-board stored compressed air due to its poor energy capacity and the thermal losses resulting from the expansion of the gas.

These days, using the patent pending 'K'Air Generator', converted to work as a compressed-gas motor, the project should be launched in 2010, thanks to a North American group of investors, but for the purpose of developing first a green energy power system. [22]

MDI

In the original Nègre air engine, one piston compresses air from the atmosphere to mix with the stored compressed air (which will cool drastically as it expands). This mixture drives the second piston, providing the actual engine power. MDI's engine works with constant torque, and the only way to change the torque to the wheels is to use a pulley transmission of constant variation, losing some efficiency. When vehicle is stopped, MDI's engine had to be on and working, losing energy. In 2001–2004 MDI switched to a design similar to that described in Regusci's patents (see below), which date back to 1990.

It has been reported in 2008 that Indian car manufacturer Tata was looking at an MDI compressed-air engine as an option on its low priced Nano automobiles. [23] Tata announced in 2009 that the compressed-air car was proving difficult to develop due to its low range and problems with low engine temperatures.

Quasiturbine

The Pneumatic Quasiturbine engine is a compressed-air pistonless rotary engine using a rhomboidal-shaped rotor whose sides are hinged at the vertices.

The Quasiturbine has demonstrated as a pneumatic engine using stored compressed air. [24]

It can also take advantage of the energy amplification possible from using available external heat, such as solar energy. [25]

The Quasiturbine rotates from pressure as low as 0.1 atm (1.47psi).

Since the Quasiturbine is a pure expansion engine, while the Wankel and most other rotary engines are not, it is well-suited as a compressed fluid engine, air engine or air motor. [25]

Regusci

Armando Regusci's version of the air engine couples the transmission system directly to the wheel, and has variable torque from zero to the maximum, enhancing efficiency. Regusci's patents date from 1990. [26]

Team Psycho-Active

Psycho-Active is developing a multi-fuel/air-hybrid chassis which is intended to serve as the foundation for a line of automobiles. Claimed performance is 50 hp/litre. The compressed air motor they use is called the DBRE or Ducted Blade Rotary Engine. [27] [28]

Defunct air engine designs

Conger motor

Milton M. Conger in 1881 patented and supposedly built a motor that ran off compressed air or steam that using a flexible tubing which will form a wedge-shaped or inclined wall or abutment in the rear of the tangential bearing of the wheel, and propel it with greater or less speed according to the pressure of the propelling medium. [29]

See also

Related Research Articles

<span class="mw-page-title-main">Engine</span> Machine that converts one or more forms of energy into mechanical energy (of motion)

An engine or motor is a machine designed to convert one or more forms of energy into mechanical energy.

<span class="mw-page-title-main">Pump</span> Device that imparts energy to the fluids by mechanical action

A pump is a device that moves fluids, or sometimes slurries, by mechanical action, typically converted from electrical energy into hydraulic energy.

<span class="mw-page-title-main">Reciprocating engine</span> Engine utilising one or more reciprocating pistons

A reciprocating engine, also often known as a piston engine, is typically a heat engine that uses one or more reciprocating pistons to convert high temperature and high pressure into a rotating motion. This article describes the common features of all types. The main types are: the internal combustion engine, used extensively in motor vehicles; the steam engine, the mainstay of the Industrial Revolution; and the Stirling engine for niche applications. Internal combustion engines are further classified in two ways: either a spark-ignition (SI) engine, where the spark plug initiates the combustion; or a compression-ignition (CI) engine, where the air within the cylinder is compressed, thus heating it, so that the heated air ignites fuel that is injected then or earlier.

<span class="mw-page-title-main">Turbine</span> Rotary mechanical device that extracts energy from a fluid flow

A turbine is a rotary mechanical device that extracts energy from a fluid flow and converts it into useful work. The work produced can be used for generating electrical power when combined with a generator. A turbine is a turbomachine with at least one moving part called a rotor assembly, which is a shaft or drum with blades attached. Moving fluid acts on the blades so that they move and impart rotational energy to the rotor. Early turbine examples are windmills and waterwheels.

<span class="mw-page-title-main">Wankel engine</span> Combustion engine using an eccentric rotary design

The Wankel engine is a type of internal combustion engine using an eccentric rotary design to convert pressure into rotating motion. The concept was proven by German engineer Felix Wankel, followed by a commercially feasible engine designed by German engineer Hanns-Dieter Paschke. The Wankel engine's rotor, which creates the turning motion, is similar in shape to a Reuleaux triangle, with the sides having less curvature. The rotor spins inside a figure-eight-like epitrochoidal housing around a fixed-toothed gearing. The midpoint of the rotor moves in a circle around the output shaft, rotating the shaft via a cam.

<span class="mw-page-title-main">Compressed-air car</span> Vehicle that uses a motor powered by stored compressed air.

A compressed-air car is a compressed-air vehicle powered by pressure vessels filled with compressed air. It is propelled by the release and expansion of the air within a motor adapted to compressed air. The car might be powered solely by air, or combined with other fuels such as gasoline, diesel, or an electric plant with regenerative braking.

<span class="mw-page-title-main">Air compressor</span> Machine to pressurize air

An air compressor is a machine that takes ambient air from the surroundings and discharges it at a higher pressure. It is an application of a gas compressor and a pneumatic device that converts mechanical power into potential energy stored in compressed air, which has many uses. A common application is to compress air into a storage tank, for immediate or later use. When the delivery pressure reaches its set upper limit, the compressor is shut off, or the excess air is released through an overpressure valve. The compressed air is stored in the tank until it is needed. The pressure energy provided by the compressed air can be used for a variety of applications such as pneumatic tools as it is released. When tank pressure reaches its lower limit, the air compressor turns on again and re-pressurizes the tank. A compressor is different from a pump because it works on a gas, while pumps work on a liquid.

An actuator is a component of a machine that produces force, torque, or displacement, usually in a controlled way, when an electrical, pneumatic or hydraulic input is supplied to it in a system. An actuator converts such an input signal into the required form of mechanical energy. It is a type of transducer. In simple terms, it is a "mover".

<span class="mw-page-title-main">Compressor</span> Machine to increase pressure of gas by reducing its volume

A compressor is a mechanical device that increases the pressure of a gas by reducing its volume. An air compressor is a specific type of gas compressor.

<span class="mw-page-title-main">Compressed-air vehicle</span> Car that uses pneumatic motors

A compressed-air vehicle (CAV) is a transport mechanism fueled by tanks of pressurized atmospheric gas and propelled by the release and expansion of the gas within a pneumatic motor.

<span class="mw-page-title-main">Quasiturbine</span>

The Quasiturbine or Qurbine engine is a proposed pistonless rotary engine using a rhomboidal rotor whose sides are hinged at the vertices. The volume enclosed between the sides of the rotor and the rotor casing provide compression and expansion in a fashion similar to the more familiar Wankel engine, but the hinging at the edges allows the volume ratio to increase. A geometrical indetermination of the Quasiturbine confinement stator shape allows for a variety of profiles and design characteristics. Unlike vane pumps, in which vane extension is generally important and against which the pressure acts to generate the rotation, the Quasiturbine contour seals have a minimal extension and the rotation does not result from pressure against these seals.

<span class="mw-page-title-main">Retarder (mechanical engineering)</span> Device for slowing down large vehicles

A retarder is a device used to augment or replace some of the functions of primary friction-based braking systems, usually on heavy vehicles. Retarders serve to slow vehicles, or maintain a steady speed while traveling down a hill, and help prevent the vehicle from unintentional or uncontrolled acceleration when travelling on a road surface with an uneven grade. They are not usually capable of bringing vehicles to a standstill, as their effectiveness diminishes as a vehicle's speed lowers. Instead, they are typically used as an additional aid to slow vehicles, with the final braking done by a conventional friction braking system. An additional benefit retarders are capable of providing is an increase in the service life of the friction brake, as it is subsequently used less frequently, particularly at higher speeds. Additionally, air actuated brakes serve a dual role in conserving air pressure.

<span class="mw-page-title-main">Rotary-screw compressor</span> Gas compressor using a rotary positive-displacement mechanism

A rotary-screw compressor is a type of gas compressor, such as an air compressor, that uses a rotary-type positive-displacement mechanism. These compressors are common in industrial applications and replace more traditional piston compressors where larger volumes of compressed gas are needed, e.g. for large refrigeration cycles such as chillers, or for compressed air systems to operate air-driven tools such as jackhammers and impact wrenches. For smaller rotor sizes the inherent leakage in the rotors becomes much more significant, leading to this type of mechanism being less suitable for smaller compressors than piston compressors.

<span class="mw-page-title-main">Hydraulic motor</span> Machine converting flow into rotation

A hydraulic motor is a mechanical actuator that converts hydraulic pressure and flow into torque and angular displacement (rotation). The hydraulic motor is the rotary counterpart of the hydraulic cylinder as a linear actuator. Most broadly, the category of devices called hydraulic motors has sometimes included those that run on hydropower but in today's terminology the name usually refers more specifically to motors that use hydraulic fluid as part of closed hydraulic circuits in modern hydraulic machinery.

<span class="mw-page-title-main">Hydraulic pump</span> Mechanical power source

A hydraulic pump is a mechanical source of power that converts mechanical power into hydraulic energy. Hydraulic pumps are used in hydraulic drive systems and can be hydrostatic or hydrodynamic. They generate flow with enough power to overcome pressure induced by a load at the pump outlet. When a hydraulic pump operates, it creates a vacuum at the pump inlet, which forces liquid from the reservoir into the inlet line to the pump and by mechanical action delivers this liquid to the pump outlet and forces it into the hydraulic system. Hydrostatic pumps are positive displacement pumps while hydrodynamic pumps can be fixed displacement pumps, in which the displacement cannot be adjusted, or variable displacement pumps, which have a more complicated construction that allows the displacement to be adjusted. Hydrodynamic pumps are more frequent in day-to-day life. Hydrostatic pumps of various types all work on the principle of Pascal's law.

<span class="mw-page-title-main">Mekarski system</span>

The Mekarski system was a compressed-air propulsion system for trams invented by Louis Mékarski or Louis Mékarsky in the 1870s. He worked in France, was born in 1843 in Clermont-Ferrand of Polish origin. Many references to him use the Polish name Ludwik Mękarski.

Angelo Di Pietro is an engine designer who developed the Di Pietro Motor air engine.

<span class="mw-page-title-main">Yaw system</span>

The yaw system of wind turbines is the component responsible for the orientation of the wind turbine rotor towards the wind.

<span class="mw-page-title-main">Rotary actuator</span> AE motor

A rotary actuator is an actuator that produces a rotary motion or torque.

<span class="mw-page-title-main">Internal combustion engine</span> Engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber

An internal combustion engine is a heat engine in which the combustion of a fuel occurs with an oxidizer in a combustion chamber that is an integral part of the working fluid flow circuit. In an internal combustion engine, the expansion of the high-temperature and high-pressure gases produced by combustion applies direct force to some component of the engine. The force is typically applied to pistons, turbine blades, a rotor, or a nozzle. This force moves the component over a distance, transforming chemical energy into kinetic energy which is used to propel, move or power whatever the engine is attached to.

References

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  17. ↑ See Compressed-air car#Energine
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